Adjustable dockboard



June 16, 1964 R. H. PFLEGER ETAL 3,137,017

ADJUSTABLE DocKBoARD 7 Sheets-Sheet 1 Filed June 26, 1963 Rahm H Ffzegez .Raber' 5.3517751 J. rk.

June 16, 1964 R. H. PFU-:GER ETAL 3,137,017

ADJUSTABLE DocKBoARD '7 Sheets-Sheet 2 Filed June 26, 1965 is SDE/e212 CCR5-mar' June 16, 1964 R. H. PFLEGER ETAL 3,137,017

ADJUSTABLE DOCKBOARD 7 Sheets-Sheet 5 Filed June 26, 19,63

mw Rabaz HFfZeger 3 :beni ERE-mar' gf www R. H. PFLEGER ETAL ADJUSTABLE DOCKBOARD June 16, 1964 '7 Sheets-Sheet 4 Filed June 26, 1963 Eaben IPfZegaz-f 3' Robert EL l amer s i a? www June 16, 1964 R. H. PFLEGER ETAL. 3,137,017

ADJUSTABLE DOCKBOARD 7 Sheets-Sheet 5 Filed June 26, 1965 Barbari H. Pfleger abar D. amer' a N V mm m. S Q

June 16, 1964 R. H. PFLEGER ETAL 3,137,017

ADJUSTABLE DocKBoARD 7 Sheets-Sheet 6 Filed June 26, 1963 33 aber@ C. amer af fm June 16, 1964 R. H. PFLEGER ETAL 3,137,017

ADJUSTABLE DOCKBOARD 3,137,017 ADJUSTABLE DOCKEARD `Robert H. Pfleger and Robert C. Ratner, Milwaukee, Wis.,

assignors to Kelley Company, lne., Milwaukee, Wis., a corporation of Wisconsin Filed .lune 26, 1963, Ser. No. 291,601 17 Claims. (Cl. 11i-71) This invention like that of application Serial No.

.177,598, tiled March 5, 1962, and now abandoned, of

which this is a continuation-in-part, relates to adjustable dockboards adapted for installation on loading docks to `span the gap between the dock and the bed of a truck or edge of the ramp is ilush with the top of the dock. The

ramp thus may occupy a cross-traffic position flush with the top of the dock, and it may be downwardly or upwardly inclined to accommodate trucks of different floor or bed heights. A biasing means, generally a group of heavy coil springs, acting through a pivoted lever arm, at all times urges the ramp upwardly, but is restrained from doing so, by a manually releasable hold-down device.

The extension lip which is hinged to the front edge of the ramp may be swung from a pendent position hanging down in front of the ramp to a positively defined elevated operative or working position forming substantially an extension of the ramp. Means are provided for rais ing the extension lip to a position somewhat short of its deiined fully elevated working or operative position, and

an automatically operating lip holding device serves to hold the lip in this partially elevated position. This position is high enough to assure engagement of the lip with the bed of a carrier in position in front of the dockboard as the ramp is lowered from its raised position. Preferably, the means which raises the extension lip functions' automatically as the ramp is raised by its spring.

' To use the dockboard, the truck or carrier to be loaded` or unloaded is backed into position in front of the dockboard with the rear edge of its iloor or bed in juxtaposition to but spaced form the dock by the bumpers on the dock. The hold-down device is then released whereupon the -ramp swings to its raised position and, at the same time,

Vthen simply walks out onto the ramp to lower it. This brings the extension lip down onto the carrier bed and,

as a result of the relative motion which takes place be tween the extension lip and the ramp as the lip moves to its defined fully raised or working position, the lip-holding means is released. The extension lip, and hence the front of the ramp, is now supported only by the bed of the carrier.

vThe dockboard is now ready for use and it should be noted that it makes no dillerence what the relative heights of the carrier bed and dock might be. The ramp with its extension lip bridges the gap between the dock and the carrier bed, whether the carrier bed is above or belowdock level. Also, it should be understood that the ramp will float up and down with the changing height of the carrier bed as the loading or unloading proceeds.

When the dockboard is not being used to load or unload a carrier, it should occupy a horizontal cross-trahie position flush with the top of the dock, so that material handling equipment, such as fork-lift trucks or the like United States Patent O may be driven across the ramp as they travel over the dock. This, of course, requires that the ramp be solidly supported in its cross-tralic position. Heretofore, the eX- tension lip was used for this purpose and, to enable it to do so, the supporting structure or framework of the dockboard was provided with an upwardly facing and forwardly projecting ledge at such an elevation that when the edge of the lip in its pendent position rested on the ledge, the ramp was at its proper cross-traic elevation.

Although the use of the hinged extension lip to support the ramp in its vcross-traffic position was generally satisfactory, the danger of damage to the extension lip by the corner of a truck striking the same during inept handling of the truck, made it desirable to provide more protected structure to support the ramp in its cross-traic position. The fulfillment of this objective is one of the purposes of the present invention.

With this objective in mind, it is an object of this invention to provide a ramp support which includes a movable strut or leg that is biased to an operative position in which itrsupports the ramp in its cross-traffic position, but from Vwhich position it is moved in consequence of elevation of the hinged lip so that the ramp may assume a downwardly inclined position to permit loading or unloading of a` Vthe hinged extension lip and thereby moving the strut or leg `out of its operative position so that the ramp: can be pushed down to provide an openingv into the building be- .tween the ramp and the bottom edge of the closed door above the ramp, thisI invention has as another object the provision of means by which the strut or leg is positively held against being swung out of its operative position as long as the ramp is in its cross-trafiic position.y Another feature of this invention thus resides in the fact that it requires at least partial elevation of the ramp to free the strut or leg for movement out of its ramp supporting position, which of course is not possible when the door above the ramp is closed. p

Since the supporting strut or leg, whether it be mounted on the ramp structure or'on the stationary mounting structure of the dockboard, must bear against an abutment xed with respect to the other structure in order to support the ramp in'its cross-traffic position, and since this is possible only if the movable strut or leg is in itsI operative position aligned withthat abutment, and since the strut or leg will be held out of its operative position until the extension lip drops to its pendent position, it follows that whenever the ramp is left in a downwardly inclined condition-no matter how slight the angle may be-in consequence of the pulling-away of a truck having a floor height less than dock level, a serious hazard exists, unless `some means isprovided to support the ramp against `further descent, or at least the permitted descent is safely the extent the ramp can be caused to Ydropor in other words, to limit unintentional descent of the ramp, when the same is left in a position other than cross-traffic, and epccially when it is left in a below-dock-level condition.

VWith the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described, and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of the physical embodiment of the invention,

constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

FIGURE l is a perspective view of a dockboard ernbodying this invention, illustrating the same in its unmounted condition, i.e. not installed on a loading dock;

FIGURE 2 is` a cross sectional view through a loading dock with an adjustable dockboard embodying this invention installed thereon, and with the ramp in its horizontal cross-traffic position;

FIGURE 3 is a sectional view through the front end portion of the dockboard on an enlarged scale, showing the ramp elevated preparatory to being lowered to its Working or operative position, and also showing the manner in which the supporting strut or leg (actually two of them, one at each side of the ramp) is held out of its operative position by the elevated extension lip;

FIGURE 4 is a view similar to FIGURE 3, but showing the ramp in a downwardly inclined below-dock-level condition, and illustrating how the safety feature of the invention selves to limit unintentional descent of the ramp when it is left in such condition; Y

FIGURE 5 is a fragmentary detail View of the holddown mechanism by which the ramp is rcleasably held against elevation;

FIGURE 6 is 'a side View of a dockboard equipped with a modified embodiment of the invention, the biasing springs and associated mechanism by which the ramp is elevated, the hold-down means and the means for lifting and holding the extension lip in its partially raised position being omitted for the sake of clarity;

FIGURE 7 is a sectional view through the front end portion of the dockboard illustrating a modified embodiment of this invention wherein unintentional descent of the ramp is safely limited when the ramp is left in an above-dock-level condition as well as when it is left in a lbeloW-dock-level condition;

indicated generally bythe numeral 12, is hingedly connected to swing up and down.

FIGURE 8 is a sectional view through the front end portion of the dockboard illustrating still another modified embodiment of this invention wherein means are provided to prevent unauthorized entry into the building by raising the hinged extension lip, forcing the ramp down, and crawling through the space thus created between the bottom of the door of the Vbuilding and the top ofthe lowered ramp; and

FIGURE 9 is a perspective view of the lower end portion of one of the ramp supporting struts or legs to better illustrate the structure by which the ramp is secured against being forced down below its cross-traffic position.

Referring now particularly to the accompanying drawings in which like numerals indicate like parts throughout the several views, the numeral 5 designates a stationary mounting structure which constitutes the frame of the dockboard. This frame or stationary structure may be constructed in any suitable manner, but is preferably built of structural steel. It has -parallel front and rear members 6 and 7 connected by parallel side rails 8 and a pair of closely spaced center rails 9, and

7 at its rear, a plurality of upright members 10 collectivelyA support a cross member 11 to which a ramp structure,

The ramp structure, like the frame or stationary structure is preferably built up of structural steel including a plurality of parallel longitudinal rails 13 having their front ends welded or otherwise fixed to a front plate 14, and their rear ends similarly secured to a rear plate 15. A steel plate or deck 16 Welded or otherwise secured to the top of the rails 13, and also preferably welded to the front and rear plates 14 and 15, completes the ramp structure. The hinge 17 connecting the two structures, i.e. the ramp structure and the stationary structure, has its complementary parts secured to the cross member 11 and to the rear plate 15.

At its frontv edge, the ramp structure has an extension lip 18, hinged thereto as at 19, to swing from a pendent position hanging down in front of the ramp to an elevated working or operative position substantially forming an extension or continuation of the deck 16 of the ramp. The hinge 19, which connects the lip with the front edge portion of the ramp, is made up of lengthwise inter-engaging tubes 20 and 21 respectively fixed to the underside of the hingedv lip and to the front plate 14, with a pintle 22 extending through the inter-engaging tubes to connect the same.

The hinge 19 is of the knuckle-joint variety, due to the fact that the rear edge of the lip engages the front edge of the ramp deck when the lip is in its raised working' position, so that the lip cannot be raised beyond this point. Accordingly, in use, when the hinged lip comes to rest upon the bed of a carrier, the front of the ramp will be supported by the carrier.

When the dockboard is installed on a'loading dock, the entire structure is set into a shallow pit 23 formed in the dock 24, with the hinged rear edge of the ramp flush with the top of the dock and its front end adjacent to the front of the dock. Hence, the ramp may occupy a cross-traffic position flush with the top of the dock, Aand may be tilted downwardly to bring its front edge down to the level of the floor of a truck or other carrier in position in front of the dock, in the event the lioor of the carrier is below-dock-level, or it may be raised to a substantial angle above dock level.

The ramp is biased upwardly by means of a group of heavy tension springs 25 anchored at one end to a bracket 9 fixed to the center rails at the rear end thereof, and having their opposite ends connected to a lever arm 26 which has one end thereof hingedly connected to the center rails 9. The opposite free end of the lever arm mounts a roller 27 which bears against the bottom edge of a cam-plate 28 fixed to the underside of the ramp. Hence the springs acting through the pivoted lever arm, and bearing against the cam plate impart an upward thrust to the ramp, tending at all times to raise the same to an upwardly inclined position extending a substantial distance above-dock-level.

However, the ramp may be held in any lowered position by means of a hold-down service, indicated generally by the numeral 29. This hold-down device may be like that of the pending application Serial No. 107,976, filed May 5, 1961, in which event it comprises a pair of cooperatingrods 30 and 31, the former having one end pivotally connected to the center rails 9 of the stationary frame structure, and the latter having one end connected to the underside of the ramp through a spring 32 enclosed within a cylindrical casing 32. A unidirectional clutch or brake device 33 holds the rods 30 and 31 against endwise separation,y without however interfering with their movement toward one another.

As shown in FIGURE 5, the brake device comprises an inclined cam 33 fixed with respect to the rod 30 and a locking roller'adapted to be wedged between this cam vand the other rod 31, the slope of the cam 33 being such as to effect release of the Wedging engagement of the roller during movement of the rods towards one another.

The hold-down device thus does not interfere with lowering of the ramp against the upward bias imparted thereon by the springs 25, but it does prevent upward movement of the ramp by the springs 25. It should be noted, though, that the spring 32 through which the rod 31 is connected with the ramp, will yield and permit the ramp to be raised by the bed of a truck or other carrier Vupon which the hinged extension lip 1S rests as the truck bed is lifted by the rear springs of the truck when the load thereon is lessened. Y

The unidirectional clutch or brake device 33 is manually releasable to enable the ramp to be raised by the springs 25; and for this purpose a releasing arm 34 ex- `tends from the brake device and has a releasing cable 35 attached to its free end and leading to a point above the ramp where it is readily accessible.

The hinged extension lip 1S is automatically raised or elevated in consequence of upward movement of the ramp, and for this purpose a lip-lifting lever 36 is pivoted Vto the front plate 14 of the ramp, with one end thereof projecting forwardly and provided with rollers 37, to bear against the underside of the lip upon downward movement of the opposite end of the lever 36. To effect such downward movement, `a cable 38 connects this end of the lever with the stationary frame structure.

Since the extension lip must be held in an elevated position to assure its resting upon the bed of a carrier in position in front of the dockboard as the ramp is lowered toits working position; a lip holding device, generally designated by the numeral 39 is provided. This lip holding device, and for that matter the lip lifter 36, may be like that of the aforesaid pending application.

Hence, the lip holding device 39 is an arm pivoted to the front plate 14 of the ramp, as is the lip lifter 36, and a torsion spring 36 reacting between the lip lifter 36 and the arm 39 swings the latter into its operative lip holding oposition as the lip is lifted. Preferably though not necessarily, the end of the arm 39 engages behind a lug 18 on the underside of the lip when in its lip holding position.

In any event, the lip holding device or arm 39 supports the extension lip in a raised position somewhat short of its fully operative or working position, so that the lip may be lifted beyond the position in which it is supported by the lip holding device 39. This additional upward motion of the lip is utilized to effect disengagement of the lip holding device during lower of the ramp to its operative or working position, so that when the truck or carrier on the bed of which the lip rests, pulls p away from in front of the dockboard after the loading or unloading operation is completed, the lip automatically drops to its pendent position. For a more detailed explanation of howthe lip lifting and holding devices function, reference may be had to the aforesaid copending application.

The main feature of this invention resides in the structure by which the ramp is supported in its crosstratic position flush with the top of the dock. The structure by which this is accomplished consists essentially of a pair of struts or legs 40, pivotally supported at the underside of the ramp, directly behind its front plate 14, to set or rest upon a pair of lixed posts 41 secured in the front corners of the stationary frame or supporting structure. The combined height of each post and its respective strut or leg is such that, when the struts or legs set upon the posts, the ramp will be in its cross-traffic position flush with the top of the dock.

Each ofthe struts or legs 40 is biased to its operative position in alignment with its respective xed post 41, by

means of a torsion spring 42. These torsion springs are coiled about the hinge pins 43 which hingedly connect the struts or legs with the ramp, and the operative upright positions of the struts or legs is defined by the engagement of their front faces with stops on the back of the front plate 14 of the ramp.

effective and reliable manner,

As long as the struts or legs are held in their operative positions by their springs 43, they will engage or seat upon the tops of the posts and thus properly support the ramp in its cross-trahie position. However, since the ramp may have to assume a downwardly inclined below-dock-level position in order to accomodate Va carrier having a floor or bed lower than dock level, means are provided to hold the struts or legs 40 out of their operative positions during the lowering of the ramp onto the bed of the carrier. The means for eiecting this purpose comprises an ar-m 44 projecting forwardly from the upper portion of each strut or leg 40, through a hole 45 in the front plate 14 of the ramp, to lie in the path of an abutment 46 fixed to the extension lip. Preferably the abutments 46 are rollers mounted on the outer ends of short arms welded to the adjacent hinge tubes 20.

The disposition of the abutments 46 and the arms 44 is such that, as the extension lip is Vswung towardits raised position, the abutments 46 push down on the arms 44 and thereby swing the struts or legs rearwardly out of line with the posts 41. It follows, therefore, that as long as the extension lip ,is in an elevated or raised position, the struts or legs 40 are held out of alignment with the posts, or in other words, are in an inoperative position permitting the ramp to assume a downwardly inclined position below-dock-level.

It also follows that as soon as the truck or carrier pulls away and the extension lip drops to its pendent position, the struts or legs are free to be brought back to their operative positions by their tension springs 43, and will be restored to their operative positions providing the front end of the ramp is ab'ove-dock-level. In this case, the application of weight on the raised ramp simply brings it to its cross-trahie position.

If the ramp is left in a beloW-dock-level condition, the forward bias imposed upon the struts or legs by the springs 43, holds the struts or legs against the rear of the posts 41, so that they snap into operative position the instant the ramp is allowed to rise above-dock-level. If this is done before a load is driven onto the ramp, everything is line, but if the ramp is left in a downwardly inclined position a very serious hazard exists, since there would be nothing to prevent the ramp from falling to the limit of its permitted descent as a load was driven onto it. The seriousness of this hazard can be appreciated when itis borne in mind that the ramp might very Well be left in a position only slightly below-dock-level. This would make it difficult for an operator of a -material-handling truck to see the danger, and if he then drove onto the ramp, a fatal accident could very Well ensue.

The present invention eliminates this danger in a very by simply providingl the front face of each of the struts or legs 40 with a plurality of downwardly facing abutments 47, each one of which is engageable with the top of its respective post 41. Preferably, these downwardly facing abutments are provided by forming saw-tooth shaped notches 4S in the front face of the struts or legs. the distance between adjacent abutments 47 and, for practical purposes, these notches are of such size that the distance between the teeth or abutments 47 is in the neighborhood of one inch or one and one-half inches. Whatever the spacing is, it is the maximum distance that the front end portion of the ramp can be caused to descend from whatever below-dock-level position in which the ramp may have been left.

Although the specific construction of the struts or legs 40 and of the posts 41 is a matter which may be left to the designer, it has been found entirely satisfactory if bothV The size of these notches determines in the cross-trafiic position of the ramp, the channels of which the posts are formed are wider than the channels forming the struts or legs, and the top of the post-forming channels are closed by plates 49, the rear edge of which forms an exposed ledge or abutment means to enter the notches 48 when the ramp is supported in a lower than cross-traflic position. f

The bottom ends of the channels forming the struts or legs are also preferably closed by plates Sii, so that the struts or legs can set upon the posts witha flat surface-tsurface engagement.

Although the invention is perhaps more practicable in the form in which it has been described thus far, and as shown in FIGURES 1 through 4, inclusive, it is possible to reverse the movable and stationary elements of the ramp-supporting structure, as shown for instance in FIG- URE 6. In this case, the struts or legs liti are pivoted to the stationary frame structure and project upwardly therefrom to have their upper ends engage the underside of downwardly facing abutments 55 on the front end portion of the ramp. These abutments 55 thus have the function of the posts 41 of the previously described construction.

As before, the struts or legs iti are biased forwardly to their operative positions in alignment with the downwardly facing abutments 55 and are swung back out of their operative upright positions in consequence of elevation of the hinged extension lip. One way in which the elevation of the lip may be used to swing the struts or legs 40- out of their operative positions comprises a cable 56 connected with each of the struts or legs 40. These cables extend rearwardly over pulleys 57 and have their opposite ends connected with levers 58 fixed to the adjacent hinge tubes 2d to swing forwardly as the extension lip is raised, and thereby impart a pull on the cables. A tension spring 60 is preferably inc rporated in each of the cables 56 to keep it taut and accommodate over-travel.

Also, as before, the struts or legs 4d have spaced abutments 47 which in this instance however face upwardly to engage the edge of the abutments 55 which project from the underside of the ramp.

Although the need for limiting unintentional descent of the ramp is most critical when the ramp is left in a below-dock-ievel condition, there are times when this is desirable even when the ramp is in an above-dock-level l condition. One way in which this can be done is illustrated in the modified embodiment of the invention shown in FIGURE 7. In this case, each strut or leg 60 has an intermediate abutment 6i which corresponds in location to the bottom of the struts or` legs it? and thus supports the ramp in its cross-traffic position when it seats upon the ixed post or abutment 41; an upper group of spaced abutments 62 to limit unintentional descent of the ramp when the same is in a below-dock-level condition; and alower group of spaced abutments 63 to safely limit unintentional descent of the ramp when the same is left in an above-dock-level condition. Preferably the struts or legs dit are offset at the intermediate abutment 61 so that this Vabutment is more pronounced than the others.

In prior dockboards wherein the hinged extension lip supported the ramp in itsVcross-trafic position, the ledge at the front of the dock upon which the free edge of the lip rested generally had a shoulder so placed that the lip could not be raised without first partially elevating the ramp. Thus, when the ramp was in its cross-trahie position, and the door of the building above the ramp was closed, it was not possible to enter the building at this point by lifting the lip and forcing'the ramp down to provide an access opening into the building under the door. To achieve the same burglar-proof feature in the structure of this invention, the struts or legs 70 (see FIGURE 8) are equipped with downwardly projecting iingers or iianges 71 so placed at the bottom ends thereof that they overlie the front faces of the posts 41v when y 8 the struts or legs are seated on the posts. This holds the struts or legs against rearward displacement, making it impossible to push the ramp down unless it is first raised high enough to have the fingers or flanges 71 clear the top of the posts di, and this cannot be done when the door 72 above the ramp is closed.

Obviously, the downwardly` projecting ngers or flanges 7l may take any desired form, but they are conveniently obtained by welding a short length of angle iron onto the bottom of each strut or leg as clearly shown in FIG- URE 9.

From the foregoing description taken in connection with the accompanying drawings it will be readily apparent to those skilled in this art that this invention provides a very significant improvement in adjustable dockboards and that it fully eliminates one of the hazards heretofore present in such dockboards.

What is claimed as our invention is:

l. Inv an adjustable dockboard for spanning the gap between a loading `dock and the bed of a carrier in loading or unloading position in front of the dock, regardless of the relative heights of the dock and carrier bed and which has stationary structure adapted to be mounted in the dock,

' structure defining a ramp having front and rear edges,

and

means hingedly connecting the ramp structure at its rear edge with a part of the stationary structure so that the ramp structure may be raised or lowered from a cross-trahie position ush with the oor of the dock on which the dockboard is installed,

the improvement which comprises safety means to limit unintentional descent of the ramp structure when its front edge is not supported by a carrier bed, said safety means comprising:

(A) a rst-supporting member associated with one of said structures facing the other structure and having exposed abutment engaging means;

(B) a second supporting member associated with said other structure having an outer end extending towards the first named structure with one side thereof engageable with said exposed abutment engaging means of the rst supporting member when the ramp structure is at an elevation at which the outer end of said second supporting member extends beyond the exposed abutment engaging means of the first supporting member;

(C) a series of abutments on said side of the second supporting member spaced apart lengthwise thereof, each separately engageable with the exposed abutment engaging means of the yfirst supporting member to support the ramp lstructure against descent when the supporting members are in cooperative relationship;

(D) means fixedly mounting one of the two supporting members with respect to its respective structure;

(E) means movably mounting the other supporting member with respect to its respective structure for movement to and from cooperative relationship with the xedly mounted supporting ember, in which relationship the side of the second supporting member is engageable with the exposed abutment engaging means of the rst supporting member;

(F) means biasing the movably mounted supporting member towards the position it occupies when the supportingmembers are in cooperative relationship; and

(G) means operatively connected with the movably mounted supporting member to move the same out of cooperative relationship with the other supporting member despite the thrust imf :to of the relative heights of the dock and carrier bed, and which has Y posed thereon by its biasing meansgto enable the ramp structure to be intentionally lowered without hindrance from said safety means. 2. In an adjustable dockboard, the structure set forth in claim 1,

(A) wherein an intermediate one ,of said series of means hingedly connectingthe ramp structure at its spaced apart abutments on the second 'supporting rear edge with a part of the stationary structure member is so positioned that when it is engaged with so that the ramp structure may be raised or lowered the` exposed abutment engaging means of the first from a cross-trafiic position fiush with the floor of supporting member, the ramp-structure is in its `the dock on which the dockboard is installed, and

cross-traffic position; and an extension lip hinged to the front edge of the ramp (B) wherein the remaining spaced apart abutments structure to swing between apendent position and comprise c. l Y an elevated position adapted to rest upon the bed (l) a first group, each one of which is separately of a carrier in position infront of the dockboard,

engageable with said exposed abutment engagthe improvement which comprises:

ing means of the first supporting member when (A) a fixed abutment on one of said structures the ramp structure is in a below-dock-level confacing the other structure and having a fiange l dition, and Y with an exposed edge;

(2) a second group each one of which is separately (B) a strut hingedly mounted upon said other engageable with said exposed abutment engagstructure for movement to and from a position ing means when the ramp structure is in an of alignment with the fixed abutment, in which above-dock-level condition. position the strut is engageable with the abut- 3. In an adjustable dockboard` for spanning the gap ment to support the ramp structure in its crossbetween a loading dock and the bed of a carrier in loadtraffic position; ing or unloading position in front of the dock, regardless (C) means biasing the strut to its said position of of the relative heights of the dockrand carrier bed, and alignment with the abutment; and which has (D) motion transmitting means operatively constationary structure adapted to i be mounted in the necting the strutlwith the hinged extension lip dock," a 1 to swing the strut out of said position of alignj structure defining a ramp having front and rear edges, ment with the abutment in consequence of means hingedly connecting the ramp structure atits movement of the hinged extension lip toward rear edge with a part ofthe stationary structure so its elevated position and to release the strut that the ramp structure may be raised or lowered for return to its said position when the lip asfrom a cross-traic position flush with the lfloor of sumes its pendentposition. the dock on which the dockboard is installed, and '35 6. In an adjustable dockboard, the structure set forth an extension lip hinged to the front edge of the ramp in claim 5, further characterized by: j

structure to swing between a pendent position and a series of spaced apart abutments on the strut, each an elevated position adapted to rest upon the bed facing said fixed abutment and each separately enof a carrier in position in front of the dockboard, i gageable with the exposed edge portion of its flange the improvement which comprises: 40 when the biasing means acting upon the strut is not (A) leg means movably mounted to swing about restrained by said lip actuated motion -transmitting an axis fixed with respect to one of said strucmeans and the ramp structure is in a downwardly intures for movement to and from a defined opclined beloW-dock-level position, so that the maxierative position in which it is engageable with mum distance the ramp4 structurecan be caused to a part of the other structure to support the drop when the same is in such a position is the disramp structure in its cross-traffic position; tance the ramp structure descends before the nearest (B) means reacting between the leg means and of the spacedrabutments on the strut contacts the its associated str ucture to bias the leg means into fixed abutment. its operative position while allowing the same l 7. In an adjustable dockboard, the structure of claim lto be moved to an inoperative position; and 5, further characterized by j l (C) Vmeans operatively connecting the leg means (A) means to hold the strut from being SWllIlg Out 0f with the hinged extension lip to move the leg said position of alignment with the abutment by means to an inoperative position in consequence l'IlOVemeDt 0f the hinged XCHSOD. 1iP .foward its ofV elevation of the lip and to release the leg elevated position as long as the ramp is in its cross means for return to its operative position when traffic' POSOD, S0 aS i0 guard against entry I10 a the lip assumes its pendent position. building in which the dockboard 1s installed, by rais- 4. In an adjustable dockboard, the structure set forth -lng the extenslon. hp .and'fqfcmgthe ramp Stuctufe in daim 3J further characterized by: downwardly to provide au access space between the (A) means to guard against lowering of the ramp 'top of the ramp structure and the bottom of a closed structure below its cross-traflic position without first gisngafove the ramp vstfuctlle, Said IrlelllSV COII1- lrrilginvaung the ramp structure Said mean? shoulder means on the strutfacing in the direction opposite that in which the strut is biased to over- (1) shoilldelf means o n the leg, means facmg m lap the adjacent side of the fixed abutment and the dlrectlon OPPOSlte that m Whlch he leg hold the strut against being swung from its posi- Y means is biased and overlapping the adjacent portion of the part of said other structure which stationary structure adapted to be Vmounted in the dock, Y l structure defining a ramp having front and rear edges,

tion of alignment with the fixed abutment. 8. In an adjustable dockboard for spanning the gap the leg means engages when the leg means is in its dened operative position, to restrain the leg means against movement out of said defined 7 operative position as long as the ramp is in between a loading dock and the bed of a carrier in loading or unloading position in front of the dock, regardless of the relative heights of the dock and carrier bed, and which has stationary structure adapted to be mounted in the dock, structure defining a ramp having front and rear edges, means hingedly connecting the ramp structure at its rear edge with a part of the stationary structure so l. l that the ramp structure may be raised or lowered from a cross-traffic position ush with the iloor of the dock on which the dockboard is installed, and

an extension lip for the ramp structure movably mounted at the front edge thereof for movement between an operative position forming substantially an extension of the ramp structure to rest upon the bed of a carrier in position in front of the dockboard and an inoperative position in which it is not engageable with the bed of a carrier so positioned,

the improvement which comprises (A) an upwardly facing abutment fixed with respect to the stationary structure;

(B) a supporting leg; Y

(C) means hingedly mounting the supporting leg at the underside of the ramp structure for movement from an operative position in line with the xed abutment, in which Vposition the supporting leg may rest upon the abutment and support the ramp structure in its cross-trafiic position, to an inoperative position out of line with the fixed abutment allowing the ramp structure to occupy a downwardly inclined position below dock level;

(D) means to bias the supporting `leg its operative position; and i (E) coacting means operatively connected between the extension lip and the supporting leg to swing the leg to its inoperative position against the bias thereon concomitantly with movement of the extension lip to its operative position and to hold the leg in its inoperative position until the lip returns to its inoperative position.

9. In an adjustable dockboard, the structure of claim 8, wherein the coacting meansrto swing the leg to its inoperative position comprises:

(A) an abutment xed with respect to the hinge lip near its hinge axis to swing in an arcuate path as the lip is swung to an elevated position, and

(B) an arm projecting from the leg into the path of said abutment to' be engaged thereby. v

l0. In an adjustable dockboard, the structure of claim 9, further characterized by the following:

(A) the ramp structure has a front rail, and

(1) the hinged connection between the extension lip and the ramp structure is at the upper front portion of said rail, and

(2) the rail has a hole beneath the hinge of the lip; and

(B) the leg is located directly behind the front rail,

and

(1) its arm projects forwardly through the hole in the rail to be engaged by the abutment which is lixed with respect to the hinged lip.

1l. In an adjustable dockboard for spanning the gap between a loading dock and the bed of a carrier in loading or unloading position in front of the dock, regardless of the relative heights of the dock and carrier bed, and which has stationary structure adapted to be mounted in the dock,

structure defining a ramp having front and rear edges,

means hingedly connecting the ramp structure at its rear edge with a part of the stationary structure so that the ramp structure may be raised or lowered from a cross-traic position flush with the floor of the dock on which the dockboard is installed, and

an extension lip for the ramp structure movably mounted at the front edge thereof for movement between an operative position forming substantially an extension of the ramp structure to rest upon the bed of a carrier in position in front ofthe dockboard and an inoperative position in which it is not engageable with the bed of a carrier so positioned,

the improvement which comprises (A) a downwardly facing abutment on the ramp structure;

(B) a supporting leg;

(C) means hingedly mounting the supporting leg to swing about an axis fixed with respect to the stationary structure for movement from an operative upright position in line with said downwardly facing abutment, inY which position the supporting leg is engaged by the abutment and supports the ramp structure in its cross-trahie position, to an inoperative position out of line with said abutment allowing the ramp structure to occupy a downwardly inclined position below-dock-level; (D) means to bias the supporting leg to its operative position; and (E) coaeting means operatively connected between the extension lip and the supporting leg to swing the leg to its inoperative position against the bias thereon concomitantly with movement of the extension lip to its operative position and to hold the leg in its operative position until the lip returns to its inoperative position. l2. In an adjustable dockboard for spanning the gap between a loading dock and the bed of a carrier in loading or unloading position in front of the dock and which has n stationary structure adapted to be mounted in the dock,

structure defining a ramp having front and rear edges, and means hingedly connecting the ramp structure at its rear edge with a part of the stationary structure so that the ramp structure may be raised and lowered from a crosstraiiic position iush with therfloor of the dock on which the dockboard is installed, the improvement which comprises:

(A) an abutment ixed with respect to one of said structures and facing the other structure; t

(B) a strut mounted to swing about an axis fixed with respect to said other structure Vfor movement to and from a position of alignment with the fixed abutment, in which position the strut is engageable with the abutment to support the ramp in its cross-trafc position;

(C) anextension member movably mounted at the front edge of the ramp structure for movement between an inoperative position to an operative position in which it forms an extension of the ramp structure and enables the dockboard to bridge the gap between the dock and a carrier in place to be loaded or unloaded; and

(1) movement of said member `from its first to its second position being necessary to enable the dockboard to bridge the gap between the dock and a carrier in place to be loaded or unloaded; and

(D) motion transmitting means operatively connected with the strut and with said member to automatically eifect swinging of the strut out of said position of alignment with the abutment in consequence of movement of said member from its inoperative position to its operative position and to effect return of said strut to its position of alignment with the abutment in consequence of movement of said member back to its inoperative position.

13. In an adjustable dockboard for spanning the gap between a loading dock and the kbed of a carrier in loading or unloading position in front of the dock, and which has stationary structure adapted to be mounted in the dock, structure defining a ramp having front and rear edges, means hingedly connecting the ramp structure at its rear edge with a part of the stationary structure so that the ramp structure may be raised and lowered from a crosstraic position flush with the oor of the dock on which the dockboard is installed, and an extension lip for the ramp structure movably mounted at the front edge thereof for movement to and from an operative position forming substantially an extension of the ramp structure to rest movable member.

13 v upon the bed of a carrier in position in front of the dockboard, safety means to limit unintentional descent of the ramp structure to a small safel increment, said safety means comprising:

(A) cooperating ramp supporting members on said structures;

(B) abutment engaging means on one of said members;

(C) a series of spaced abutments on the other one of said members all facing in the same direction and separately engageable with said abutment engaging means to support the ramp structure against descent beyond a level depending upon which of the spaced abutments is engaged with said abutment engaging means;

(D) means movably mounting one of said members on its respective structure for movement between a first position at which the safety means is operative and a second position at which the safety means is inoperative and intentional descent of the ramp structure v is possible; v

(E) means biasing said movable member to itslrst position; and l (F) control means operatively connected with said movable member and with the extension lip to effect movement of said member to its second position concomitantly with movement of the extension lip to itsl operative position forming substantially an extension of the ramp structure and to release said movable member for return to its first position when the eX- tension lip assumes its inoperative position.

14. In an adjustable dockboard, the structure set forth in claim 13, wherein the spaced abutrnents are on the 15. Inlan adjustable dockboard, the structure of claim 14, wherein the movable member is on the ramp structure.

'16. In an adjustable dockboard for spanning the gap between a loading dock and the bed of a carrier in loading or unloading position in front of the dock, and which has stationary structure adapted to be mounted in the dock,

Y structure defining a ramp having front and rear edges,

means hingedly mounting the ramp structure at its rear Y edge for up and down swinging movement with respect to the stationary structure so that the ramp structure may be raised and lowered from a cross traffic position ush with .the iioor of the dock upon which the dockboard is installed, and an extension lip for the ramp structure movably mounted at the front edge thereof for movement to and from an operative position forming substantially an extension of the ramp structure, to rest upon the bed of a carrier in position in front of the dockboard, safety means to limit unintentional descent of the ramp structure to a small, safe increment, said safety means comprising:V

(A) ramp structure supporting means comprising cooperating elements on said structures,

(l) one of said elements having a series of spaced apart abutments, and

(2) the other element having a part engageable withany one of said spacedv apart abutments when said cooperating elements are in cooperative relationship, whereby said elements coop- Y erate to support the ramp structure at an elevation depending upon which of said spaced abutments is engaged with said part;

(B) means movably mounting one of said elements for movement to and from its potentially operative position;

(C) biasing means acting upon said movable element and yieldingly holding it in its potentially operative position; and

(D) control means operatively connected with the extension lip and operable upon said movable element to move the same out of and hold it against return to its potentially operative position as long as the extension lip is in its operative position forming au extension of the ramp structure v to thereby prevent ramp structure supporting engagement i between said elements and enable intentional descent of the ramp structure, and to release said movable element for return to its potentially operative position when the extention lip is moved out of its operative position.

17. In an adjustable dockboard, the structure set forth in claim l6, but wherein Y (A) the movable element of the ramp structure supporting means Vhas its mounting Xed with respect to the stationary structure, and wherein (B) said movable element is arranged to swing between an upright potentially operative position and an inclined inoperative position. v

No v references cited.

UNITED STATES PATENT OFFICE CERTIFICATE OE CORRECTION Patent No., 3, 137,017 June 16, 1964 Robert Hg. Pfleger et al It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l, line 47, for "form" read from --9 column `4, line 58, for uservice" read device column 5, line 47, for "lower" read lowering column 6, line 30, for "tension" read torsion-w column l2, line 44, v for "to" read and line 49, beginning with "(1) movement of said" strike out all to land including "and" in line 53, same column l2,l

Signed and sealed this 27th day of October 1964.,

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attcsting Officer Commissioner of Patents 

1. IN AN ADJUSTABLE DOCKBOARD FOR SPANNING THE GAP BETWEEN A LOADING DOCK AND THE BED OF A CARRIER IN LOADING OR UNLOADING POSITION IN FRONT OF THE DOCK, REGARDLESS OF THE RELATIVE HEIGHTS OF THE DOCK AND CARRIER BED AND WHICH HAS STATIONARY STRUCTURE ADAPTED TO BE MOUNTED IN THE DOCK, STRUCTURE DEFINING A RAMP HAVING FRONT AND REAR EDGES, AND MEANS HINGEDLY CONNECTING THE RAMP STRUCTURE AT ITS REAR EDGE WITH A PART OF THE STATIONARY STRUCTURE SO THAT THE RAMP STRUCTURE MAY BE RAISED OR LOWERED FROM A CROSS-TRAFFIC POSITION FLUSH WITH THE FLOOR OF THE DOCK ON WHICH THE DOCKBOARD IS INSTALLED, THE IMPROVEMENT WHICH COMPRISES SAFETY MEANS TO LIMIT UNINTENTIONAL DESCENT OF THE RAMP STRUCTURE WHEN ITS FRONT EDGE IS NOT SUPPORTED BY A CARRIER BED, SAID SAFETY MEANS COMPRISING: (A) A FIRST UPPORTING MEMBER ASSOCIATED WITH ONE OF SAID STRUCTURES FACING THE OTHER STRUCTURE AND HAVING EXPOSED ABUTMENT ENGAGING MEANS; (B) A SECOND SUPPORTING MEMBER ASSOCIATED WITH SAID OTHER STRUCTURE HAVING AN OUTER AND EXTENDING TOWARDS THE FIRST NAMED STRUCTURE WITH ONE SIDE THEREOF ENGAGEABLE WITH SAID EXPOSED ABUTMENT ENGAGING MEANS OF THE FIRST SUPPORTING MEMBER WHEN THE RAMP STRUCTURE IS AT AN ELEVATION AT WHICH THE OUTER END OF SAID SECOND SUPPORTING MEMBER EXTENDS BEYOND THE EXPOSED ABUTMENT ENGAGING MEANS OF THE FIRST SUPPORTING MEMBER; 